A Clockwork Orange (1971)

Mono:

The UHD blu-ray's AC-3 mono track is exactly the same as the old 1999 Warner DVD's mono track, but 3.9 dB louder.

Recall that the 1991 Warner LaserDisc is veiled and less detailed.

5.1:

The 5.1 mix on the UHD is ostensibly a new mix, although it may well be the old 5.1 mix mastered (very) differently and with changes in various scenes. It's best to just refer to it as a new mix since it's different enough to be designated so.

The centre channel on the UHD is much less rolled-off than the old blu-ray centre channel, and it has a lot more real detail. The old centre channel is veiled and distant, but the new one, although more revealing of distortion (especially across dialogue), is more natural and lifelike. There's a lot of information above 8 kHz that simply didn't exist in the old surround mix's centre.

The left and right channels in the UHD 5.1 mainly differ from the old blu-ray's left and right channels in dialogue-driven scenes: dialogue from the centre channel is now spread ambiently to the left, right, surround left, and surround right channels. This is evident in the spectrals below - you can see that many sections that were empty in the old L/R and SL/SR channels now contain sound. The UHD has surround left and surround right channels that are louder relative to the other channels. The L, R, SL, and SR channels are darker-sounding (bassier) than in the old 5.1.

The LFE of both blu-rays isn't really a 'real' LFE; it contains a surprising amount of high-frequency content, and if one were to listen to it in isolation it often sounds like an ordinary non-LFE channel. The UHD mutes most sections of the movie but is otherwise similar.

Centre:

Left / Right:

Surround left / Surround right:

LFE:

I've read observations from people, some even from professional reviewers, that the new 5.1 track is flawed. Frankly, I disagree; I think it sounds good. Most complain about it being brighter, which I imagine is based on the new centre channel having its high frequencies much less rolled-off. I prefer it. I don't care much for the ambient dialogue now in the surround channels, but the centre channel's 'unveiling' is by far the biggest change here, and it is an improvement.

I wish the mono, on the other hand, sounded better. It's bizarre to read people wishing in the weeks leading to the UHD's release that Warner would include the "old DVD's mono" track, because while it does sound okay, it almost certainly could sound better. A company like Warner should be held to a higher standard and be expected to create a new audio transfer from their assets (which we have no reason to believe have simply disappeared!) after over twenty years since last doing so.

I'm curious if the analogue track on Warner's '80s LaserDisc sounds different.

A Clockwork Orange (1971)

The 5.1 remix (the only mix on the blu-rays) is a legitimate, discrete mix that generally has much better fidelity than the original mono mix.

But it's far from perfect. For whatever silly reason, ambient sound has been added to EVERY scene that played mostly silent in the original mix, so scenes that don't contain music now have what sounds light street noise and wind underlying them. Bizarrely, this applies to both outdoor and indoor scenes.

The music also seems far too loud in the remix relative to the dialogue.

The original mono mix was issued in 1991 by Warner on LaserDisc and later on DVD (R1, R2, R3, and R4). The LaserDisc doesn't sound very good. Its high frequencies are attenuated and it sounds like it's an analogue generation removed from the old R2 DVD I was able to find.

The mono track on the DVD reveals that the original mono mix is a more cohesive, well-balanced mix and I prefer it overall despite its generally inferior sound quality (music, mostly). It has some crazy bass! If it weren't for the unusually heavy degree of compression applied to it (no doubt inherent in the mix itself), I wouldn't hesitate to call it truly excellent. Again, its music levels are better balanced relative to everything else, and the entire thing just sounds right.

The PAL DVD also plays at the correct pitch and tempo, so I assume it's an NTSC-to-PAL convert (I didn't bother to verify this).